# 02_jes2001_wave1.R
# Purpose: Ideological Extremism and Political Participation in Japan
# Created: 2020-5-16 Taka-aki Asano
# Last Modified: 2021-10-9

# package
require("haven")
require("dplyr")
require("ltm")
require("plink")


# dataset
JES2001 <- read.table(
  "JESIII/Japanese/0530β.dat", 
  header = TRUE, sep = "\t", quote = "\"", comment.char = ""
)
JES2001$ID <- 1:nrow(JES2001)


# respondent
JES2001_Respondent <- JES2001[,c("ID", paste0("A", 15:20, "S1"))]
colnames(JES2001_Respondent)[-1] <- paste0("q", 15:20 )
JES2001_Respondent <- apply(JES2001_Respondent, c(1, 2), 
                            function(x) {
                              if(x%in%c(8, 9)) {x <- NA} 
                              else {x <- x}}
) %>% as.data.frame()


# IRT
## handle missing data
JES2001_Respondent <- JES2001_Respondent[rowSums(JES2001_Respondent[,-1], na.rm = TRUE) != 0,]

## estimate item parameters
irt2001 <- ltm::grm(JES2001_Respondent[,-1], IRT.param = FALSE)
irt2001 ## viewing

## estimate voters ideology
score2001_Respondent <- ltm::factor.scores(irt2001, JES2001_Respondent[,-1])


# rescale
## common item
common2012 <- c("q8", "q9", "q10", "q12", "q13")
common2001 <- c("q15", "q19", "q16", "q17", "q18")
index <- data.frame(
  group1 = match(common2012, colnames(JES2012_Respondent[,-1])), 
  group2 = match(common2001, colnames(JES2001_Respondent[,-1]))
)

## list of parameters
### 2012
res2012 <- coef(irt2012)
res2012 <- res2012[,c(4,1:3)]
colnames(res2012) <- c("a","b1","b2","b3")
### 2001
res2001 <- coef(irt2001)
res2001 <- res2001[,c(4,1:3)]
colnames(res2001) <- c("a","b1","b2","b3")
### merge
pm <- list(res2012, res2001)

## list of scale
rescat <- list(rep(4, nrow(res2012)), 
               rep(4, nrow(res2001)))

## as.irt.pars
pm2012 <- as.poly.mod(n = nrow(res2012), model = "grm", 
                      items = 1:nrow(res2012))
pm2001 <- as.poly.mod(n = nrow(res2001), model = "grm", 
                      items = 1:nrow(res2001))
res <- as.irt.pars(pm, common = index, cat = rescat, 
                   poly.mod = list(pm2012, pm2001), 
                   location = FALSE)

## list of voters' position
ideology <- list(score2012_Respondent$score.dat$z1, 
                 score2001_Respondent$score.dat$z1)

## rescale
plink_out <- plink(res, common = index, base.grp = 1, 
                   rescale = "MS", ability = ideology)
summary(plink_out)

## estimate voters ideology (rescale)
score2001_Respondent_plink <- link.ability(plink_out)$group2
JES2001_Respondent$Ideology <- -1 * score2001_Respondent_plink


# LDP's position
JES2001_LDP <- JES2001[,c("ID", paste0("A", 15:20, "S3X1"))]
colnames(JES2001_LDP)[-1] <- paste0("q", 15:20 )
JES2001_LDP <- apply(JES2001_LDP, c(1, 2), 
                     function(x) {
                       if(x%in%c(8, 9)) {x <- NA}
                       else {x <- x}}
) %>% as.data.frame()
JES2001_LDP <- JES2001_LDP[rowSums(JES2001_LDP[,-1], na.rm = TRUE) != 0,]
score2001_LDP <- ltm::factor.scores(irt2001, JES2001_LDP[,-1])
ideology <- list(score2012_Respondent$score.dat$z1, 
                 score2001_LDP$score.dat$z1)
plink_out <- plink(res, common = index, base.grp = 1, 
                   rescale = "MS", ability = ideology)
JES2001_LDP$Ideology <- -1 * link.ability(plink_out)$group2


# DPJ's position
JES2001_DPJ <- JES2001[,c("ID", paste0("A", 15:20, "S3X2"))]
colnames(JES2001_DPJ)[-1] <- paste0("q", 15:20 )
JES2001_DPJ <- apply(JES2001_DPJ, c(1, 2), 
                     function(x) {
                       if(x%in%c(8, 9)) {x <- NA}
                       else {x <- x}}
) %>% as.data.frame()
JES2001_DPJ <- JES2001_DPJ[rowSums(JES2001_DPJ[,-1], na.rm = TRUE) != 0,]
score2001_DPJ <- ltm::factor.scores(irt2001, JES2001_DPJ[,-1])
ideology <- list(score2012_Respondent$score.dat$z1, 
                 score2001_DPJ$score.dat$z1)
plink_out <- plink(res, common = index, base.grp = 1, 
                   rescale = "MS", ability = ideology)
JES2001_DPJ$Ideology <- -1 * link.ability(plink_out)$group2
